Such illumination systems are known per se. They are used, inter alia, as luminaire for general lighting purposes, for example, for office lighting, for shop lighting or, for example, for in-home general lighting purposes.
The luminescent material generally absorbs part of the light emitted by a light source of the color-tunable illumination system and converts the absorbed light into light of a different color. The luminescent material is often arranged at a distance from the light source. This configuration is also referred to as a remote phosphor configuration. A benefit when using the remote phosphor configuration is that the conversion efficiency and the life-time of the luminescent material are improved and that the range of luminescent materials to choose from is improved.
Such a color-tunable illumination system is known from US 2005/0041424. In an embodiment of the known color-tunable illumination system the illumination system comprises at least a first blue light emitting diode emitting light having the color blue, and at least a second blue light emitting diode emitting light having the same color blue. The known illumination system comprises luminescent material which is arranged in so called carrier material. The carrier material is arranged in strips covering portions of a housing which surrounds the first and second light emitting diodes. The strips of carrier material may be arranged such that the illumination from at least one of the light emitting diodes is projected through the carrier material. By modulating the power of the separate light emitting diodes, the illumination conditions can be adapted, thus tuning a color of the known illumination system.
A disadvantage of the known illumination system is that light emitted from the known illumination system creates colored shadows.